1. Field of the Invention
The present invention relates to a source-channel combined coding method, which applies scalable video coding (SVC) video to a digital video broadcasting-satellite 2 (DVD-S2) broadcasting service to reduce rain attenuation while minimizing a structural change of a satellite broadcasting system and, and a satellite broadcasting system using the same.
2. Description of the Related Art
Recently, satellite broadcasting technology has been replaced with a high-performance digital transmission scheme which is able to realize a high sound quality and provides various additional services. Therefore, existing DVB-S systems are being developed into DVB-S2 systems capable of performing high-speed transmissions, interactive data transmissions, and high-quality video transmission.
The service environment of satellite broadcasting is significantly influenced by rainy weather conditions. Therefore, the availability of satellite broadcasting may be reduced during bad weather conditions.
FIG. 1 is a graph showing results obtained by measuring the rain attenuation characteristics of a Ka-band transponder of KOREASAT-3, depending on frequencies. Referring to FIG. 1, it can be seen that an attenuation width increases with a rain concentration rate. In particular, an attenuation characteristic in the 20 GHz band is approximately three times larger than an attenuation characteristic in the Ku band.
In Korea, two thirds of annual precipitation is concentrated on four months of the summer season. Therefore, the quality reduction of satellite broadcasting services caused by rain attenuation is very severe during this time. Recently, research has been reported several times, reporting that the climate of Korea is changing to a subtropical climate. Due to such a change in climate pattern, the average level of annual precipitation is increasing considerably. In reality, the precipitation level between 2003 and 2007 increased by 302.18 mm, compared with precipitation between 1993 and 1997. The rain attenuation value in Seoul alone, during the past five years, has increased by 7.78 dB, as compared with the rain attenuation value between 1990 and 1999.
In order to address such a rain attenuation effect, research has been conducted into a power control method, a fixed compensation method, and an adaptive transmission method. More specifically, research into a variable beam pattern satellite broadcasting system is being conducted by the NHK research laboratory in Japan. The variable beam pattern satellite broadcasting system partially increases transmitted power only in a region in which intense localized rainfall is occurring, using a phased array fed reflector antenna, and compensates for attenuation. DirecTV in the US increases link availability by increasing the equivalent isotropically radiated power (EIRP) of satellites.
Since the above-described transmitted power and beam control methods must be considered when a satellite is designed and manufactured, to be implemented, these methods require a new satellite which satisfies the requirements, and an additional cost for realizing the technology inevitably increases. Therefore, research needs to be conducted into an effective method which is capable of solving the rain attenuation problem while minimizing the structural change of the existing satellite broadcasting system.
Meanwhile, as a video compression technique, there is provided an SVC scheme which is capable of providing an adaptive video service to various environments.
The SVC scheme, which is an extended coding scheme of H.264, has been developed to solve problems such as the fact that scalability based on the SVC scheme attempted by the existing MPEG-2 and MPEG-4 schemes has low compression efficiency, composite scalability cannot be supported, and there are difficulties in implementing the scheme.
The SVC scheme refers to technology which codes several video layers into a single bit stream. The layers may include one base layer (BL) and a plurality of enhancement layers (EL) which may be consecutively stacked on the base layer. Based on lower layer information, each of the enhancement layers may express a bit rate, a frame rate, and resolution, all of which are allocated to the enhancement layer, to the maximum. In the SVC scheme, as the number of enhancement layers to be stacked increases, a variety of bit rates, frame rates, and resolutions may be supported. Therefore, the SVC scheme is suitable for a multimedia contents service under a universal multimedia access (UMA) environment which is capable of handling various problems such as a diversity of bandwidth in a heterogeneous network, a diversity of performance and resolution in receiver terminals, and the various preferences of content consumers.